It is known that a 7-[4-substituted-3-{(cyclopropylamino)methyl}-1-pyrrolidinyl]quinolone carboxylic acid derivative not only is safe and has a strong antibacterial activity, but also exhibits a strong antibacterial activity to resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), penicillin-resistant Streptococcus pneumoniae (PRSP), and vancomycin-resistant Enterococcus (VRE) (Patent Literature 1).
An aqueous liquid formulation having a pH that is higher or lower than the physiological pH sometimes provides stimuli when administered. Hence, it is preferable to design an aqueous liquid formulation which has a pH around the physiological pH, that is, a near-neutral pH, when designing an aqueous liquid formulation such as an injectable formulation. Patent Literatures 2 to 7 disclose an aqueous liquid formulation in which a quinolone carboxylic acid derivative is contained as a principal agent and which is neutral pH. These literatures disclose a formulation in which the precipitation of the principal agent is suppressed and the principal agent is solubilized by adding polyvalent metal such as magnesium into a solution (Patent Literatures 2 to 7).
On the other hand, there is known an aqueous liquid formulation in which a solution containing a quinolone carboxylic acid derivative as a principal agent is adjusted to be slightly acidic, around pH 4, thereby to improve the chemical and physical stability of the principal agent (Patent Literatures 8 to 9). Patent Literature 9 discloses a formulation which includes a lyophilized formulation containing quinolone carboxylic acid and a dilution liquid containing a polyvalent metal compound.
It is noted that the above-described quinolone carboxylic acid derivative disclosed in Patent Literatures 2 to 9 does not have a cyclopropylaminomethyl structure.